This is the final phase of a multivariate young adult follow-up study of several samples of boys with Hyperkinetic/Attention Deficit Disorder (HK/ADD), of their nonhyperkinetic full brothers, and of nonhyperkinetic volunteer classmates. All patients were originally evaluated at ages 6 to 12 as referrals to the University of Iowa child psychiatry clinic; all were diagnosed as HK/ADD by child psychiatry faculty/residents' all were treated eitiher pharmacologically (primarily with methylphenidate) or psychologically (primarily with short-term parent and/or teacher counseling); and all are being followed up by the present investigator at adolescence (ages 12-18) and/or young adulthood (ages 21-23). The main samples are: a) an Early Medicated group (HK/ADD boys diagnosed between 1967-1972 and treated with methylphenidate for an average of 3 years); b) a Transitional Medicated group (HK/ADD boys diagnosed between 1972-1975 and also treated with methylphenidate); c) a Transitional Unmedicated) group (HK/ADD boys also diagnosed between 1972-1975 but, because of physician preference, not treated with psychotropic drugs); and d) a Late Unmedicated group (HK/ADD boys diagnosed between 1975-19788 and not treated with psychotropic drugs). By the end of the present grant period, a total of 421 boys (160 Early Medicated patients, 40 Transitional Medicated patients, 22 Transitional Unmedicated patients, 37 Late Unmedicated patients, 104 brothers, and 58 classmates) will have been seen within two years after their 21st birthday and administered a multitrait and multimethod battery of tests, questionnaires, and interviews. In addition, 146 consecutively-referred, playroom-diagnosed boys and their 100 normal controls will be followed up at between 18 to 20 years of age. The general aim of the present study is to describe the life course of the HK/ADD child and to identify the individual predictors (e.g., aggression, IQ) and the environmental predictors (e.g., treatment, parenting styles) of differences in life course. Results of a series of multivariate analyses will provide a detailed description of a variety of outcomes among both medicated and unmedicated HK/ADD boys as adolescents and young adults, with classmate and sibling controls. Planned comparisons will test the effects on these outcomes of hyperkinesis per se; of stimulant drug treatment; and of response to medication. Establishing means for predicting and diagnosing residual ADD/adult MBD will be a special concern.